1. Field of the Invention
The present invention is related to an anti-interference antenna of a wireless tire pressure receiver, and more particularly to an antenna integrated into a power cable of the wireless tire pressure receiver, having electromagnetic interference shielding (EMI-shielding) against interference from power wires in the power cable.
2. Description of the Related Art
Tires are critical parts of vehicles. Contact between a road surface and a vehicle is through tires. Functions of tires are to absorb shocks caused by irregularities of the road surface by means of air pressure and to provide good traction to the road surface. Abnormal tire pressure arising from underinflation, air leakage or overinflation, fails to secure the functions of tires and what is worse could be life-threatening to drivers and passengers.
Therefore, constant monitoring of tire pressure is a must for ensuring that tires are under proper working conditions. To facilitate drivers constantly monitoring tire pressure of tires of vehicles, each tire of new vehicles is equipped with a wireless tire pressure meter periodically and wirelessly transmitting detected tire pressure to a wireless tire pressure receiver inside the vehicles. By means of the analysis and display of the wireless tire pressure receiver, tire pressure information of each tire can be constantly provided to drivers to facilitate drivers taking preventive measure upon encountering abnormal tire pressure.
To receive the signals transmitted from all wireless tire pressure meters, the wireless tire pressure receiver is equipped with a built-in antenna. As the size of the wireless tire pressure receiver is not sizable and the mounting position thereof is not fixed, the signal-receiving intensity may not be perfect. To enhance the signal-receiving intensity of a wireless tire pressure receiver, with reference to FIGS. 15 and 16, a conventional wireless tire pressure receiver has a box 1, an internal antenna 2, a circuit board 3, a socket 4 and a power cable 5. The internal antenna 2 is mounted inside the box 1. The circuit board 3 is mounted inside the box 1 to connect with the internal antenna 2. The socket 4 is mounted to one corner of the box 1. One end of the power cable 5 is mounted through the socket 4 to connect with a cigarette lighter of a vehicle and supply an operating power to the circuit board inside the box.
The antenna 2 extends to the socket 4. An external antenna 51 is sheathed by the power cable 5. The other end of the power cable 5 is plugged in the socket 4 through a plug 52 so as to form a power supply loop. The external antenna 51 is connected with the internal antenna 2 inside the wireless tire pressure receiver so as to extend the length of the internal antenna 2.
Such approach certainly improves the signal-receiving intensity of the wireless tire pressure receiver. However, as power wires and the antenna are both sheathed in the power cable and current flows through the power wires and the external antenna, electromagnetic interference therebetween is inevitable. Once interference occurs, normal operation of the wireless tire pressure receiver is affected.
Although using the power cable of the conventional wireless tire pressure receiver to sheath the antenna therein does extend length of the built-in antenna, an effective approach in eliminating electromagnetic interference needs to be further addressed.